Radial velocity curves of Gaia-4 and Gaia-5

Here we present RV follow-up observations of 28 M and K stars with candidate astrometric substellar companions, which led to the confirmation of two systems, Gaia-4b and Gaia-5b, identification of five systems that are single lined but require additional data to confirm as substellar companions, and the refutation of 21 systems as stellar binaries.

Gaia-4b is a massive planet (M=11.8+/-0.7M_J_) in a P=571.3+/-1.4d orbit with a projected semimajor axis a0=0.312+/-0.040mas orbiting a 0.644+/-0.02M_{sun}_ star. Gaia-5b is a brown dwarf (M=20.9+/-0.5M_J_) in a P=358.62+/-0.20d eccentric e=0.6423+/-0.0026 orbit with a projected angular semimajor axis of a0=0.947+/-0.038mas around a 0.34+/-0.03M_{sun}_ star. Gaia-4b is one of the first exoplanets discovered via the astrometric technique, and is one of the most massive planets known to orbit a low-mass star.